A gamma characteristic is a non-linear relationship that approximates the relationship between encoded luminance in a system (such as a television display) and the actual desired image brightness. Displays that may require a more linear relationship between encoded luminance and image brightness can use what is commonly referred to as “gamma correction” to provide a more desirable image for display.
One type of display device that can benefit from gamma correction is an Active Matrix Organic LED (AMOLED) based display which may be relatively efficient compared to TFT-LCD based displays, as an AMOLED based display may more faithfully reproduce images including slight variations in luminence between pixels. However, one of the challenges associated with providing images on an AMOLED based display is that slight variations in the voltages generated by drivers may be manifested in the image displayed by the AMOLED based display.
One approach for driving data to an AMOLED based display is commonly referred to as “gamma buffered driving,” which is depicted in FIG. 1. As shown in FIG. 1, a gray voltage generator 110 that is configured to generate N gray voltage levels provided to a gamma buffer 120. The N gray voltage levels represent the range of luminence values that can be provided on any particular channel of a display. The gamma buffer 120 amplifies the respective gray voltage level to provide gamma corrected luminence values so that image quality is maintained in view of the gamma characteristics of the display. A plurality of selectors 122 select the gamma corrected gray voltage levels to be driven to a respective channel (CH1-CHM) based on digital data provided to the selector 122.
According to the gamma buffered driving approach shown in FIG. 1, different loading on the different channels (Ch1-ChM) may introduce variations between voltage levels driven to the respective channels. Furthermore, if the gamma buffered driving approach shown in FIG. 1 is used to drive a high definition display, the size of the gamma buffer 120 may need to be large (i.e., N may be large).
Another approach to driving data to a display is commonly referred to as “channel buffered driving,” a representation of which is shown in FIG. 2. According to FIG. 2, the gray voltage generator 110 generates N gray voltage levels each of which is provided to each of the selectors 122. As described above in reference to FIG. 1, the selector 122 selects the appropriate luminence value presented by the gray voltage levels based on the digital data provided to the selector 122. The outputs of the selectors 122 are provided to channel buffers 130 each of which is coupled to a channel of the display. Because each channel has a dedicated buffer included in the channel buffer 130, the loading effects discussed above in reference to FIG. 1 may be reduced. However, variations between the buffers included in the channel buffer 130 may introduce differences between the voltage levels driven on the different channels.